Several diseases and water-quality problems can look alike. Sudden deaths, falling feed intake or breathing distress need prompt advice from a qualified aquatic animal health professional and an appropriate diagnostic laboratory.
What it is
Physical damage can allow shell-eroding microbes to contribute to lesions. Fungal involvement and environmental damage are also possible. This guide concerns live farmed shrimp, not post-harvest blackening of chilled product.
A superficial lesion may change at moulting, but deep or spreading damage, lost appendages or reduced feeding requires investigation. Apparent improvement after moulting does not fix an unhealthy pond bottom.
Signs to watch for
- Brown or black patches, pits or eroded areas on the shell.
- Darkened or damaged appendages, antenna tips or tail edges.
- Severe cases may include deeper tissue damage, weakness or reduced feeding.
What else can look similar?
- Fungal lesions, injury-related melanisation and environmental irritation.
- Other causes of body marks; shell colour alone cannot identify a pathogen.
Spread & risk factors
- Opportunistic organisms from the pond can enter or worsen damaged surfaces.
- Abrasive handling, crowding, poor feeding conditions and dirty bottoms increase risk.
How to confirm the cause
- A professional should assess depth and distribution of lesions and arrange microscopy, culture or tissue examination when needed.
- Check oxygen, nitrogenous wastes, feed access and recent handling. Do not select treatment from a photograph of a black spot.
Prevention: your practical checklist
Avoid rough netting and unnecessary transfers; maintain gear without sharp or abrasive surfaces.
Match stocking and feed access to the system’s capacity and prevent injuries from crowding.
Control feed waste and bottom accumulation, and maintain stable water conditions.
Assign nets, trays and boots to each pond; clean and disinfect equipment under the farm’s biosecurity plan.
Keep seed-batch, feeding, water-quality and mortality records so a change is noticed early.
What to do if you suspect a problem
Record lesion location, frequency, feeding response and daily deaths.
Seek examination if lesions spread, deepen or accompany poor feeding or mortality.
Correct measured management problems and reassess after moulting with your professional.
Keep affected stock, equipment and water separate. Agree on safe disposal and any harvest or discharge with your professional.
What not to do
- Do not call all black spots Fusarium or assume every lesion needs antibiotics.
- Do not force moulting or use unapproved chemical baths from old manuals.
- Do not mix medicines or pond chemicals on guesswork; use only legally permitted inputs under qualified advice.
Farmer questions
Will the next moult solve it?
Some superficial shell damage may be shed, but deeper infection and the conditions causing injury may remain. Keep investigating persistent or worsening cases.
Are black spots on harvested shrimp the same problem?
Not necessarily. Post-harvest melanosis is a separate handling and quality issue. This guide addresses lesions observed in live cultured shrimp.
Sources & further reading
Sources support the discussion above. Their inclusion does not mean these organisations reviewed or approved this article. Some references cover other shrimp species; the guide states limitations where relevant.
- 01Better Management Practices for shrimp farms ↗
Marine Products Export Development Authority (MPEDA)
- 02Disease prevention and health management in coastal shrimp culture — interpreting external signs ↗
FAO; historical training guidance
- 03Diseases of Penaeid Shrimps in the Philippines — Shell Disease ↗
SEAFDEC Aquaculture Department, Manual No. 16; historical penaeid reference, not treatment instructions
AI-assisted source check: 16 October 2026, not professional approval. Reference dates refer to the documents, not their URL filenames or live disease status.
AquaGrow completed an AI-assisted technical-source and translation-consistency check on 16 October 2026. This is educational content, not an individual pond diagnosis, a prescription or an endorsement by ICAR-CIBA, NACA or WOAH. An independent clinical review has not been completed. Translations also await independent review by native-speaking aquaculture specialists.
This is a selected learning library, not a complete disease list or a statement that every condition occurs in Andhra Pradesh or Odisha. No live outbreak surveillance is provided.